Communications apparatus for downloading data

Abstract: The invention prevents unauthorized use of data in communications. When terminals (2) with different data transmission rates are simultaneously connected to a host computer (1), the host computer (1) sets a single common data communication rate to all the terminals (2) to assure synchronization. The host computer (1) sends a data body to each terminal (2) over an unilateral communications link (3) in a cyclic manner while a bilateral communications link (4) is established between the host computer (1) and each terminal (2). Response to an individual request from each terminal (2), the host computer (1) downloads descrambling data for descrambling and a loader for executing the data body. The host computer (1) determines from among the terminals (2), any terminal (2) having a communications means that sets the lowest data transmission rate, and sets the data transmission rates of the terminals (2) simultaneously connected thereto to the lowest rate.

Description: The present invention is directed to a novel communications apparatus that scrambles data to be communicated in order to prevent unauthorized use of the data in wired or wireless communications. Thanks to advanced data transmission technology, we can enjoy communications between personal computers in an easy manner over public telephone line or dedicated line. Radio digital signal transmission technology is now matured enough to allow PCM communications to be in widespread use. When data to be communicated is open to public free of charge, no consideration is given to secrecy requirement of the data. Thus, the data are subjected to no particular maneuver for this requirement; attaching packet number and error correction code onto the data to be communicated may be sufficient. Since information is gaining more and more its significance in today's information environment, data that need protection are increasing accordingly. Conventionally, data to be communicated is coded by an encoder prior to transmission. A receiver has a decoder that decodes encoded data the receiver has received. The encoding and decoding are performed according to a predetermined communication protocol. The encoder for encoding data to be communicated has a cryptographic program for encoding the data according to predetermined sequence. Once decoded, however, the data are accumulated in normal state. The user of a terminal may pay for a first use of the data. For subsequent use, however, the data may be available to the user free of charge. This allows practically unauthorized use, and presents a serious problem to an information provider at a host computer side. Such a system presents no problem if the data is of such a nature that it is at the user's disposal at the terminal once the host computer downloads the data to the terminal. Depending on the type of data, the information provider may want to bill the user for each service, that is, the downloading of the data. If the data is stored at the terminal, however, no subsequent service is requested, and thus no billing happens. IEICE TRANSACTIONS, vol.E-73, no.7, July 1990, TOKYO JP pages 1133 - 1146, XP000159229 R.MORI ET AL 'SUPERDISTRIBUTION: THE CONCEPT AND THE ARCHITECTURE' relates to an approach to distributing software in which software is made available freely and without restriction but is protected from modifications and modes of usage not authorized by its vendor. Especially, it is described that S-programs are distributed unidirectionally over various ways. WO-A-90 13865 discloses a communications apparatus including a host computer and a plurality of terminals, wherein said host computer comprises means for sending a scrambled data body, descrambling data and a loader to each terminal, a bidirectional communications link is established between said host computer and each terminal, said host computer comprises means for downloading the descrambling data for descrambling said scrambled data body and said loader for executing said data body to said each terminal in response to an individual request from each terminal, said each terminal has an external memory device for once storing said data body, said descrambling data and said loader and means for storing said descrambling data and said loader to the available space of a main memory of said terminal, and said loader has means for descrambling the scrambled data body referring to said descrambling data. Such a communications apparatus is described in the preamble of claim 1. It is an object of the present invention to provide cryptographic means that prevents repeated use of data that has been downloaded to a terminal and used once there. This allows an information provider to bill the user for each service by downloading the data. This object is solved by the features as outlined in the characterizing clause of claim 1. The dependent claims 2 to 4 relates to preferred embodiments of the communications apparatus of the present invention. In particular the present invention is characterized in that said communications apparatus further comprises a unidirectional communications link used for communicating said scrambled data body sent from said host computer to each terminal in a cyclic manner, and said external memory device has means for automatically deleting or overwriting said descrambling data and said loader stored in said external memory device after the completion of decoding and transferring of said scrambled data body and before the completion of data processing at said terminal. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a communications network system using a communications satellite. Fig.2 is a block diagram of a communications network system using CATV network. Fig.3 is a diagram showing that a terminal reads a data body, descrambling data, and a loader into its memory. Fig.4 is a diagram showing that the main memory reads the descrambling data and the loader. Fig.5 shows another embodiment, different from that of Fig.4. Referring now to the drawings, the preferred embodiments of the present inventions are discussed. Networks shown in Fig.1 and Fig.2 are employed as a data transmission network in the present invention. Fig.1 shows the network system made of a communications satellite link and a public communications network as wired link. The network system comprises a host computer 1 at an information provider, terminals 2, a communications satellite 3 and a public communication network 4 which may be digital or analogue. In the context of the present invention, it is not important whether the public communications network is digital or analogue. The host computer 1 sends unidirectionally information to any terminal while bidirectional communications take place between the host computer 1 and the terminals 2 over the public communications network 4. In this embodiment, the communications satellite is employed as radio communications link. Instead, terrestrial radio communications link is a perfectly acceptable alternative. Fig.2 shows the network system that employs CATV network. A host computer 1 is connected to each terminal via CATV network 5 of any known cable link such as optical communication link or coaxial cable link. The CATV network 5 is interactive, 6 being upline, and 7 downline. The use of an existing CATV having unidirectional communications capability only may be contemplated. In this case, however, a public network is used for the upline 6 from each terminal to the host computer 1. The data to be communicated is constructed of a (scrambled) data body, descrambling data and a loader. The host computer 1 sends numerous data bodies to the terminal 2 via the communications satellite 3 or the CATV network 5 in a cyclic manner, while the host computer 1 sends the descrambling data and the loader to the terminal 2 on demand via the public network 4. When the CATV network 5 is employed, the descrambling data and the loader are sent over a channel separate from the channel used for the transmission of the data body. In this case, the descrambling data and the loader are subjected to necessary processing, such as attaching a unique identification code, prior to their transmission. Thus, the data to be communicated are divided between two separate transmission routes; some of data bodies are so large in size that they are suited to a faster transmission rate communication, while the descrambling data and the loader are relatively small in data size, needing to identify a service requesting terminal for billing purposes. The data body to be communicated is scrambled. The descrambling data is made of scrambling parameters, a password and compressed dictionary as a type of scramble. In the context of the present invention, the data body means the one that contains an execution file and is initiated by certain command. The loader is used to initiate the data body. The loader descrambles the data body according to the descrambling data while unwinding i.e. descrambling, the data body onto the available memory space of the main memory of a terminal or an external memory device such as a hard disk unit. Then, the loader transfers control to the descrambled data. Both the descrambling data and the loader are unwinded or descrambled into the main memory and the external memory device. After the descrambling data and the loader are downloaded, the descrambling data in the external memory device is automatically deleted according to a predetermined sequence or is deleted or overwritten when the entire scrambled data is decoded or descrambled. An attempt to reinitiate the data body later is aborted without the downloading of the descrambling data from the host computer. This prevents unauthorized use of data. The same effect may be achieved if the loader is deleted or overwritten in same manner as above. The sequence of data processing by the terminal 2 is now discussed. From among the data that is transmitted via the communications satellite 3 or the CATV network 5 in a cyclic manner, a desired data body is retrieved. The retrieval of data may be performed in several methods. When the data body is transmitted in packet, each packet is preceded by an identification code indicative of the data body, and the terminal 2 specifies the identification code to retrieve the data. Identification codes may be transmitted in the form of a table in a cyclic manner so that the user may easily check them on the monitor screen of the terminal 2. The terminal 2 retrieves the desired data body, but the terminal 2 is unable to do on its own since the data is scrambled. The terminal 2 accesses the host computer 2 via the public communications network 4 or the CATV network 5 to request the downloading of the descrambling data and the loader by specifying the identification code or any code corresponding to the identification code. The terminal then retrieves the desired data body. If, in this case, correspondence between a data body and its descrambling data and loader may be implemented into a program, no input of the identification code indicative of each data body is required. Fig.3 shows the state in which a terminal 2 has read a data body, its scrambling data and loader into its memory. An external memory device such as a hard disk drive is designated 8. A memory area 9 of the main memory for executing process is already partially occupied by OS. The external memory device 8 stores the data body, the descrambling data and the loader in their own separate files. When initiation of the loader is activated via a keyboard or a mouse, the OS accesses the external memory device 8, and processes the available memory space 9 of the main memory. This state is illustrated in Fig.4. Specifically, the loader 10 and the descrambling data 11 are transferred to the available memory space 9. Also, control is transferred from the OS to the loader 10. The loader 10 reads the data body in the external memory device 8 while decoding the data body referring to the descrambling data. In the meantime, the descrambling data and the loader in the external memory device 8 are deleted. The timing of the deletion is not important as long as the deletion has been completed before completion of data processing at the terminal 2. It is perfectly acceptable that either the descrambling data or the loader is deleted in the external memory device. Also, the same effect will be achieved by migration, namely parallel operations of copy and delete, instead of the above method in which the descrambling data and the loader are once entirely copied to the memory area 9 from the external memory device 8 and then deleted at a time entirely. Fig.5 shows another type of sequence. Calling the loader in the external memory device 8 initiates reading of the loader 10 and the descrambling data 11 into the available space of the memory area 9. The loader 10 reads the data body stored in the external memory device 8 referring to the descrambling data 11, and unwinds or descrambles the data to the available memory space. In this process, the loader 8 completes at least the unwinding or descrambling of the scrambled data such as an execution file in the data body. When decoding and transferring are completed, the descrambling data and the loader are rewritten, i.e. overwritten. To receive a next service, a user is required to acquire the descrambling data and the loader again. This prevents unauthorized use of data at each terminal. It is perfectly acceptable that either the descrambling data or the loader is deleted or overwritten. In the above embodiment, substantially improved overall transmission efficiency results since large-sized data is communicated via highly efficient communications system while files for preventing unauthorized use of data are communicated via bidirectional communication networks. This arrangement also achieves improved information management at the host computer. Once the terminal 2 decodes the scrambled data body, the loader and the descrambling data, needed for decoding process, are deleted or overwritten. This prevents reinitiation of the data body. To reinitiate, the terminal 2 must request another service to the host computer 1. Thus, unauthorized use of data is prevented.

Claims: A communications apparatus including a host computer (1) and a plurality of terminals (2), wherein said host computer (1) comprises means for sending a scrambled data body, descrambling data (11) and a loader (10) to each terminal (2), a bidirectional communications link (4) is established between said host computer (1) and each terminal (2), said host computer (1) comprises means for downloading the descrambling data (11) for descrambling said scrambled data body and said loader (10) for executing said data body to said each terminal (2) in response to an individual request from each terminal (2), said each terminal (2) has an external memory device (8) for once storing said data body, said descrambling data (11) and said loader (10) and means for storing said descrambling data (11) and said loader (10) to the available space of a main memory (9) of said terminal (2), and said loader (10) has means for descrambling the scrambled data body referring to said descrambling data (11), characterized in that said communications apparatus further comprises a unidirectional communications link (3) used for communicating said scrambled data body sent from said host computer (1) to each terminal (2) in a cyclic manner, and said external memory device (8) has means for automatically deleting or overwriting said descrambling data (11) and said loader (10) stored in said external memory device (8) after the completion of decoding and transferring of said scrambled data body and before the completion of data processing at said terminal (2). The communications apparatus according to claim 1, wherein said unidirectional communications link is a satellite communications link (3). The communications apparatus according to claim 1 or 2, wherein said bidirectional communications link is a public communications network (4). The communications apparatus according to any of the preceding claims, wherein said bidirectional communications link is an interactive CATV network (5).

Inventors: TSUMURA MIHOJI, TSUMURA, MIHOJI
Applicants: RICOS KK, RICOS CO., LTD.
Application year: 1994
Main classification: H04L29
IPC codes: H04L29